Performance of an LED, particularly in a high performance optical system, is limited by the precision and consistency of the location the LED die within the LED package and to the precision of mounting the LED package on an electrical circuit board or other mounting surface. The optical centering or the precision of mounting the LED package on a mounting surface is particularly important, e.g., when secondary optics are used, such as in automotive forward lighting lamps. Conventional techniques of aligning the LED die and package are inadequate for many high performance applications.
Current methods of aligning the LED die within the package and the package to the mounting surface is based on standard semiconductor assembly techniques. Accordingly, attempts to improve the alignment accuracy of an LED die and package are focused on controlling semiconductor assembly variations. Conventional semiconductor techniques of aligning the die and package are generally inaccurate because non-LED type semiconductor applications are not concerned with light emission.
For example, conventional pick and place mounting of LED packages uses the outside edges of the LED package or the electrical leads of the package. However, the outside edges of the LED package are typically molded plastic or cast epoxy materials, which are dimensionally inaccurate. Moreover, package electrical leads are generally formed from sheet metal, which is unsuitable for high precision alignment. Thus, the positional relationship of the LED die within the package to the outside edges or leads of the LED package is generally too imprecise for high precision alignment.
Accordingly, what is needed is a system and method that improves the alignment accuracy of an LED package is desired.